The present invention relates to an overhead powerline survey method and in particular to a survey method for the design and maintenance of overhead powerlines, including survey of a line from points off the line so that the route of the line and the local topography in the vicinity of the line may be recorded.
Traditionally, surveying of existing powerlines or of the route of planned powerlines is restricted to following only the exact route of the powerline by sighting from one point on the line to the next, along the route of the line. The traditional methodology allows only very limited account to be taken of local topographical features, e.g. roads, houses and the like. Measurements taken in powerline surveys are generally recorded manually in a logbook and computed at a later time to derive two-dimensional co-ordinates for the points measured, i.e. height and distance along the line. These co-ordinates are then plotted using traditional drafting techniques. If it is required to input this data into a computerized system, the transfer has to be done manually.
The positions of the required support structures for a proposed powerline may then be defined on this plot. Then the line of the conductor is plotted and ground clearance is checked. If sufficient clearance has been obtained, this design is accepted and the relevant materials ordered so as to construct the powerline.
This paper based system has a number of inherent shortcomings. These are:
The whole design process takes place in two dimensions whereas in reality three dimensional data should be used. PA1 Modifying a proposed design is time consuming and costly. PA1 The whole process is slow. PA1 The transcription of data and manual computation of co-ordinates and drafting thereof is prone to error. PA1 The survey technique requires that a corridor along the proposed route be cleared completely of vegetation, so as to establish a clear line of sight. PA1 The survey technique does not take full account of features offset from the route of the line. PA1 The design process takes place in a scaled plot, not at actual scale, thereby introducing errors due to the poor definition of the features plotted. PA1 The conductors are modelled using fixed parameters. PA1 The cost of the proposed line is not calculated until the design has been accepted. PA1 a device for preparing two and three dimensional representations of the proposed powerline and its support structures in relation to the surrounding land; PA1 a device for defining the conductor design of the proposed powerline in relation to its surrounding environment; PA1 a device for comparing and checking the conductor design parameters against industry standards; and PA1 a device for identifying the type number and cost of each of the components required to construct the powerline. PA1 a device for checking the position of the actual line and determining the clearance between the ground profile and an existing or proposed powerline; and PA1 a device for modelling design factors such as conductor type, conductor weight, conductor tension, ambient temperature and the like. PA1 a device for recording data pertaining to the geographical position and condition of an existing powerline; PA1 a computer for in-field calculation of the tension of the powerline conductors by the measurement of the conductor sag; and PA1 a redesigning device for determining and specifying repairs or modifications needed to be made to the powerline. PA1 preparing two and three dimensional representations of the proposed powerline and its support structures in relation to the surrounding land; PA1 defining the conductor design of the proposed powerline in relation to its surrounding environment; PA1 comparing and checking the conductor design parameters against industry standards; and PA1 identifying the type, number and cost of the components required to construct the powerline. PA1 recording data pertaining to the geographical position and condition of an existing powerline; PA1 calculating in-field the tension of the powerline conductors by measuring the conductor sag; and PA1 determining and specifying repairs or modifications needed to be made to the powerline.
These cannot be easily altered to take account of varying limits.